Currently most of a variety of digital video and audio data may be downloaded through the Internet. Many people often store downloaded related file in a portable electronic product, such as smart phone, tablet computer, etc., and then watch videos directly on the portable electronic product. When watching video for long time, it is preferable to have a clamping device, or a supporting device to assist holding the portable electronic product. Currently the applicable clamping device adapted to portable electronic product usually only applies to single kind product of different dimensions, for example, 6 to 8-inch tablet computer, 3 to 5-inch smart phone . . . , the capable range difference for clamping device is small, unable to apply to a variety of products. Clamping effectiveness for some big screen products, such as tablet computer is not solid, therefore currently there is a few clamping device adapted to both the wide-screen tablet computer and rectangular mobile phone. According to the above mentioned, the disclosure of the invention provides a clamping device adapted to various types of portable electronic product.